William Optics Zenithstar 103 APO
William Optics Zenithstar 103 APOWilliam Optics Zenithstar 103 APOWilliam Optics Zenithstar 103 APOWilliam Optics Zenithstar 103 APO

William Optics Zenithstar 103 APO

£1,095.00✓ 2 year warranty


In stock shipped 1-2 working days.

About this product

Model:  wo_zs103_bu
Part Number:  A-Z103BU

The NEW William Optics Zenithstar 103 APO features an air-spaced doublet lens with an Ohara FPL-53 ED glass element and fully multi-coated optics for high resolution, high contrast images virtually free of false-colour. 

Despite it's large 103mm objective diameter it is surprisingly compact and very solid! Many airlines will accept it as carry-on luggage. An ideal size for serious observations of deep sky objects and planets.

Versatile f/6.9 native focal ratio or f/5.5 when used with matching 0.8x flattener / reducer.

Supplied with mounting rings, guiding rings and Vixen-style dovetail bar.

CNC machined aluminium for a superior fit and finish. 

Heavy duty, dual speed 2.5" 1:10 R&P focuser. A popular choice for imaging.

Available in Blue, Red or Gold anodised.  

Ohara FPL-53 vs FPL-51 ED Glass

The dispersion properties of ED and SD glass elements are important in determining the overall colour correction. The abbe index is used to quantify the 'partial dispersion' of a particular glass. Pure Fluorite offers the highest partial dispersion at around 94.99 V, Ohara FPL-53 glass is very close to Fluorite at 94.93 V and is often referred to as Synthetic Fluorite.  FPL-53 is also noticeably better than Ohara's lower spec' FPL-51 glass which offers an abbe index of 81.54 V.


  • 103mm f/6.9 Doublet air-spaced APO
  • CNC machined ultra-high precision lens cell
  • FPL-53 ED glass element for enhanced colour correction
  • 2.5" Heavy Duty, dual-speed rack & pinion focuser
  • 0.8x Reducer / Flattener available separately
  • Innovative Bahtinov mask cover included!
  • Supplied with mounting rings, guiding rings, CNC carry handle, Vixen-style dovetail bar and Bahtinov mask cover

Telescope Field of View Simulator

What's in the box

  • Telescope OTA
  • Mounting Rings
  • Guidescope Rings
  • Carry Handle
  • Vixen-Style Dovetail
  • Bahtinov Mask Cover


Aperture 103 mm
Focal Ratio F/6.9
Focal Length 710 mm
Objective Type ED Doublet, Air Spaced,
Fully Multi-Coated, SMC coating.
Lens Shade Retractable
Tube Weight 9.6lbs. (4.36 kg) - Including dovetail & rings

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